Lockout circuit incorporating electromagnetic relays

ABSTRACT

A lockout circuit is provided to prevent the operation of all but one of a plurality of interconnected reed relays. Each relay includes a two-way contact and a winding. A common resistancecapacitance circuit is employed to provide a potential to the relay winding to keep it energized during the time which elapses between the opening of a normally closed contact and the closing of a normally open contact.

United States Patent [72] Inventor Gunter l-lovorka [56] References Cited ie Austria UNITED STATES PATENTS [211 P 741,651 2,712,101 6/1955 Salati 317/136X [22] Filed July 1, 1968 P d A 6 1971 2,971,135 2/1961 Ebert 1. 317/137 $3 Q" N Stand d El t 3,066,245 11/1962 Baker et al. 317/136 1 ssgnee g 3,296,499 1/1967 Quinlan 317/154 New York, N.Y. Primary Examiner-Lee T. Hix [32] Priority July 28, 1967 Attorneys-C. Cornell Remsen, Jr., Rayson P. Morris, Percy [33] Austria P. Lantzy, J. Warren Whitesel and Delbert P. Warner 31 1 A7,015/67 [54] LOCKOUT CIRCUIT INCORPORATING RELAYS ABSTRACT: A lockout circuit is provided to prevent the awmg operation of all but one of a plurality of interconnected reed [52] US. Cl 317/136, relays. Each relay includes a two-way contact and a winding. 317/137, 317/ 154 A common resistance-capacitance circuit is employed to pro- [51] Int. Cl ..H01h 47/00 vide a potential to the relay winding to keep it energized dur- [50] Field of Search ing the time which elapses between the opening of a normally 137, 154 closed contact and the closing of a normally open contact.

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'1 P 1 C31! u I Patented April 6, 1971 6. H 0 VORKA Inventor v Attorney LOCKOUT CIRCUIT INCORPORATING ELECTROMAGNETIC RELAYS This invention relates to a lockout circuit for electromagnetic relays, having two-way contacts but no two-way makebefore-break contacts.

Lockout circuits having make-before-break contacts are known, but with reed relay such two-way make-before-break contacts cannot be employed without introducing unacceptable complexity into otherwise simple circuits.

It is an object of the invention to provide a lockout circuit which does not use two-way make-before-break contacts so that reed relays can be employed. Without eliminating the conventional relay circuits, this accomplished in that each gate of the lockout circuit comprises a relay having a two-way contact and a diode and a common energy storage circuit is provided for bridging the transit time of the two-way contacts.

In the circuit according to the invention, a relay having a two-way contact and a diode are required as individual components per gate of the circuit. Besides, a common resistancecapacitance circuit is used. Thus, the expenditure of components is not substantially higher than with known lockout circuits having two-way make-before-break contacts.

The invention will now be explained with reference to the drawing, which shows a circuit according to the invention.

The key-controlled contacts TlTn are provided with a common protective resistor Rs. The series resistor Rv serves to limit the current for charging the capacitor C. Because the discharge circuit is inhibited when a contact is closed, a residual charge could enable a short-time response of another relay. This is not desired, therefore, the resistor Rp, which is parallel to the capacitor C, is employed to completely discharge the capacitor when a relay contact I, 2n has been operated.

The following requirements are to be met by the invention:

Upon operation of any of the key-controlled contacts T1 to Tn in any desired sequence, only one relay should respond and should hold itself as long as the key is depressed. This is the relay which is associated with the contact TlTn that has been actuated first. When a plurality of keys have been actuated at the same time, only a single relay should be able to hold itself.

By way of example, the actuation of the key-controlled contact T2, will cause relay ll to operate in the following circuit: Negative terminal of voltage source-resistor R.rclosed keycontrolled contact T2-coil of relay ll-diode D2-normally closed terminals of contacts n to l-ground.

The contact 2 is now opened by the relay ll and the relay II is held by the holding circuit which includes the charged capacitor C.

Before any of the relay contacts 1 to n has operated, the capacitor C has been charged to the voltage U. When contact 2 is opened in the present example, the capacitor C will be discharged in the following circuit:

Positively charged electrode of capacitor-resistor Rvdiode DZ-coil of relay ll-key-controlled contact T2resistor Rs-negative tenninal of voltage source and negative terminal of the capacitor.

The charge which has been stored in the capacitor C is sufficient for holding relay ll during the transit time of contact 2. When contact 2 is closed on its normally open tenninal, relay ll will hold itself during the depression of the key in the following circuit:

Ground-normally closed terminal of contact lnormally open terminal of contact 2coil of relay ll-closed key-controlled contact T2resistor Rs-negative terminal of voltage source.

The energizing circuits of the relays associated with the other key-controlled contacts are now interrupted.

lf plurality of keys are actuated at the same time, a plurality of relays may respond at the same time but only one relay, usually the first in the chain, can hold itself because the holding contacts are in series.

While the principles of the invention have been described above in connection with s cific apparatus and applications, it IS to be understood that t 15 description IS made only by way of example and not as a limitation of the scope of the invention.

lclaim:

l. A lockout circuit comprising:

a direct current potential source;

a ground;

a plurality of relay circuits, each relay circuit including an electromagnetic relay, an actuable keying means connected between said electromagnetic relay and said direct current potential source, a two-way make contact connected between said electromagnetic relay and said ground, said electromagnetic relay being energizable upon actuation of said keying means, said two-way made contact providing a self-locking ground path to said relay upon actuation by the energized electromagnetic relay;

an energy storage means connected between said ground and said direct current potential source; and

a plurality of diode means respectively connected between said energy storage means and said electromagnetic relays, said diode means being poled such that current is supplied therethrough to a selected electromagnetic relay corresponding to the actuated keying means for energizing said selected electromagnetic relay during the transit time when the corresponding two-way make contact is being actuated to provide said self-locking path tosaid selected electromagnetic relays.

2. A lockout circuit in accordance with claim 1, wherein said plurality of relay circuits are connected in parallel and the plurality of two-way make contacts of said relay circuits are connected in series, a first of said two-way make contacts being connected to said ground and the last of said two-way make contacts being connected to said energy storage means, each said two-way make contact being so connected that a path is normally open between said ground and corresponding electromagnetic relay and a path is normally closed between said ground and said energy storage means for providing current to store energy in said energy storage means, and the energization of selected ones of said electromagnetic relays upon actuation of the corresponding keying means closes said normally open path of the corresponding two-way make contact to said relay and opens said normally closed path to said energy storage means.

3. A lockout circuit in accordance with claim 2, said energy storage means includes a resistor and a capacitor in a parallel circuit, and a second resistor connected in series with said parallel circuit for limiting the current through said energy storage means;

4. A lockout circuit in accordance with claim 3, wherein a third resistor is connected between said direct current potential source and respective keying means for. limiting the current through the actuated electromagnetic relay. 

1. A lockout circuit comprising: a direct current potential source; a ground; a plurality of relay circuits, each relay circuit including an electromagnetic relay, an actuable keying means connected between said electromagnetic relay and said direct current potential source, a two-way make contact connected between said electromagnetic relay and said ground, said electromagnetic relay being energizable upon actuation of said keying means, said two-way made contact providing a self-locking ground path to said relay upon actuation by the energized electromagnetic relay; an energy storage means connected between said ground and said direct current potential source; and a plurality of diode means respectively connected between said energy storage means and said electromagnetic relays, said diode means being poled such that current is supplied therethrough to a selected electromagnetic relay corresponding to the actuated keying means for energizing said selected electromagnetic relay during the transit time when the corresponding two-way make contact is being actuated to provide said self-locking path to said selected electromagnetic relays.
 2. A lockout circuit in accordance with claim 1, wherein said plurality of relay circuits are connected in parallel and the plurality of two-way make contacts of said relay circuits are connected in series, a first of said two-way make contacts being connected to said ground and the last of said two-way make contacts being connected to said energy storage means, each said two-way make contact being so connected that a path is normally open between said ground and corresponding electromagnetic relay and a path is normally closed between said ground and said energy storage means for providing current to store energy in said energy storage means, and the energization of selected ones of said electromagnetic relays upon actuation of the corresponding keying means closes said normally open path of the corresponding two-way make contact to said relay and opens said normally closed path to said energy storage means.
 3. A lockout circuit in accordance with claim 2, said energy storage means includes a resistor and a capacitor in a parallel circuit, and a second resistor connected in series with said parallel circuit for limiting the current through said energy storage means;
 4. A lockout circuit in accordance with claim 3, wherein a third resistor is connected between said direct current potential source and respective keying means for limiting the current through the Actuated electromagnetic relay. 